Yes, I think they all should do their own solo albums. They all have so much talent, it would be sad if they stopped singing. Liam's voice is amazing! Harry's voice is FANTASTIC!! Niall's voice is amazing when he's doing a solo. Louis's voice is really awesome too.
I'm not sure it would be a good idea for 1D to make their own songs. As good as they are, people who come from groups and become famous on their own are very rare. Micheal Jackson is an exception and so is Beyonce and Kelly Rowland, but these are just the minority. Zayn looks like he's doing well but to me he's only a one hit wonder with "Pillowtalk." Ashton from JLS said he would like to do his own solo singing career and where is he now? I'm not saying it's not possible but it is a HUGE risk that very few succeed in because them singing with their GROUP made them famous- NOT on their own. I am also not saying that 1D cannot do their own albums per se but I don't think they would be that big a hit.